Image orthicon tubes



Filed Dec. 15, 1966 W. ORT ET AL IMAGE ORTHICON TUBES 2 Sheets-Sheet 1 Fig] Inventors:

Werner 0r! Kurt Frank by AIM/1 Iii/w A ftorney United States Patent 3,499,197 IMAGE ORTHICON TUBES Werner Ort, Pfungstadt, and Kurt Frank, Darmstadt, Germany, assignors to Fernsek G.m.b.H., Darmstadt,

Germany Filed Dec. 15, 1966, Ser. No. 601,943 Claims priority, applicatioi Germany, Dec. 16, 1965,

Int. Cl. n'ol 9/18 U.S. Cl. 2925.16 11 Claims ABSTRACT OF THE DISCLOSURE A method of making an image orthicon tube, which includes fusing one end of an open-ended tube of large diameter onto an outwardly projecting flange at one end of a tube of smaller diameter; also includes the step of inserting through the open end of the large tube a target and other image-converter electrodes, securing the imageconverter electrodes in place in the large tube, and closing the open end of the large tube by a face plate.

The invention relates to a production method and construction for an image orthicon tube whereby the signalto-noise ratio and modulation depth in relation to the dimensions of the bulb of the tube can be improved and p in which the electrode assembly can be simplified.

The electrode system and the operation of image orthicon tubes are taken as being well-known. The most important electrodes with their abbreviations are listed below in the order in which they are arranged along the axis of the tube:

The tubular envelope to receive these electrodes comprises an elongated tubular portion with a wall at one end and an outwardly-extending flange at the other end, and a cylindrical cap of larger diameter which is fused to the flange. The end of the cap consists of the so-called face-plate to receive the photocathode and is provided with an annular metallised portion to make contact with the photocathode. The electrodes inside the cap are also known as image converter eletctrodes.

The neck of the tube contains the entire beam system and the above-mentioned wall coating, while the cap contains the electrodes, namely the photocathode, target, field mesh, and grid 4, and the evaporator systems required to produce the photocathode.

In the technique hitherto applied, the electrode systems were assembled as follows:

The frame electrodes for the field mesh, the frame electrodes for the target and the grid 6.6 were first anmounted on pins of the flange, whereupon the cap was fused on to the flange at the neck of the tubet. The beam system and secondary electron multiplier were then attached to the foot of the tube.

Only when the cap and the neck of the tube had been fused together were the target and field mesh inserted into the frame electrodes in the cap chamber. This sequence was thought necessary in order to prevent these parts from being damaged by water vapour and heat during the fusing process. For this reason firstly the target then the field mesh were introduced into the tube through its neck, placed in the frame electrodes within the cap chamber and anchored therein by means of locking springs. The beam system was finally brought into the neck of the tube and the foot of the tube was fused to the neck.

A serious drawback to this method is that the useful diameter of the target and of the field mesh must be less than the width of the neck of the tube, since the circular constructional elements that are required to form the target and to support the field mesh take up a substantial proportion of the cross-section of the neck. This means, however, that one must either use a larger bulb for the tube, so that the energy for focussing and deflecting the electron beams must accordingly be greater than is theoretically necessary, or one must accept a reduction in the quality of the image resulting from the use of a smaller raster.

In the method of making image orthicon tubes according to the invention an open-ended tube is first fused into the outwardly-projecting flange of the neck of the main tube. The electrodes for the cap chamber, including the field mesh and target are then brought through the open end of the tube and fixed to it. The open end is firmly sealed by the face plate which acts as a support for the photocathode. In the resultant image orthicon tube the external diameter of the supporting rings for the target, and possibly for the field mesh, may be larger than the diameter of the neck of the tube, and preferably of a size such that the useful diameter of the said components is equal to the diameter of the neck. This means that the quality of the signals produced by the image orthicon tube can be greatly improved. In particular the signal-tonoise ratio and modulation depth can be improved without changing the external dimensions of the tube as cornpared with known equivalent tubes. As compared with present day tubes therefore, the tubes may have a smaller bulb and a narrower neck orif the bulb is of the same size as in known tubes e.g. the 3" tube-may have a target area about larger. This represents a 38% gain in signal-to-noise ratio (interference spacing).

The grids G4 and 6.6, and the target, instead of being fixed to ceramic bars mounted on the base, or pins mounted on the flange, as in known constructions, are preferably anchored in notches in the glass wall of the bulb with the aid of springs. This results in a further saving of space and simplification of construction.

Further details and some modifications of the invention will now be explained by reference to the accompanying drawings, in which:

FIG. 1 diagrammatically illustrates the difference in production method between conventional image orthicon tubes and those according to the invention, and

FIG. 2 is a section through a dismantled image orthicon tube of the invention.

FIG. 1 shows two bulbs of image orthicon tubes, the top one 1 being provided with electrodes of a conventional size and the bottom bulb 1 'being equipped with electrodes by the method of the invention. Between the two bulbs 1 and 1' is a target 2 and a field mesh system 3. The target contains the target glass 4 and target mesh 5, each mounted on a support ring, while the field mesh system comprises a field mesh 6 also secured, as by spot welds, onto a frame. Whereas the members 2 and 3 have hitherto been inserted into the bulb in the direction of the upper arrow, i.e. through the neck of the tube, in accordance with the invention the electrodes are inserted from the open end of the bulb 1' in the direction of the lower arrow. The face plate is not illustrated here. It will be seen from the dimension of the bulbs 1 and 1' that a sub stantially smaller tubular vessel can be used in the method of the invention. This feature is very advantageous from the point of view of space-saving in the production of miniature or colour cameras where three or more image orthicon tubes are contained in one camera. The insertion of the electrodes from the open end of the bulb results in simplifications in construction and greater precision in the important spacings, with an advantageous effect on the production of orthicon tubes. These measures will be discussed in detail in connection with FIG. 2.

In FIG. 2, 6 is part of the neck of the tube, provided at the end with a flange 7 into which base or cap pins 8 are fused. Before the electrodes are fitted the flange and an open-ended cylindrical glass tube 9 are fused together at 10. On the inside of the tube 9 is a number of notches 11 which are incised into the glass wall with a narrow diamond wheel. The other electrodes shown comprise a grid 12 (G.4) with a frustoconical portion, and a spring 17 to make contact with a metallised portion 18 on the inside of the neck of the tube; a field mesh electrode 13 with a mesh 13a; a target electrode 14 with a target mesh 14a, and target glass 14b, a G.6 electrode 15, and a photocathode ring 16. The ring 16 is mounted on a glass face plate 19 subsequently used to close the bulb. Later in the tube-making process the photocathode is produced on the face plate 19.

The tube is assembled as follows:

Each individual electrode 12 to is provided on the outside with four springs 20, which taper to a point just wide enough to fit into the notches 11. The various pins 8 are provided with strip leads 21, 21a extending to a height such that their ends can be spot-welded onto the inserted electrodes. The electrodes 12 to 15 are introduced in turn and are each welded onto the associated strip lead 21 before the next electrode is inserted. In contrast to the main construction described above, where the target and the field mesh are inserted in ready-mounted holders, in this case both the target and the field mesh are fitted directly. The springs 20 engage in the notches 11 in the process, thereby attaching the electrodes accurately and in shock-proof manner in the appointed places. The end of lead 21a is joined to two 'bent wire springs 21b projecting slightly over the edge of the open end of the cylinder 9. Once the electrodes 12 to 15 have been introduced and welded onto their leads 21 the bulb 9 can be closed by the glass plate 19. The setting down of the plate 19 creates a contact between the metallised portion 16 and the ends 21b of the springs, thereby connecting the photocathode to a base pin 8. In order to seal the tubes, the plate 19, which is made narrower at the edge by faceting, and the top edge of the bulb 9, are heated at a periphery by a hot, needle-shaped flame while the top part of the tube 9 and the plate 19 are kept above the conversion temperature of glass with the aid of a stove. If the hotpointed flame is used only a very narrow part of the edge of the plate 19 and bulb 9 will be melted so that the join will, so to speak, be welded. It is advantageous for the face plate 19 together with a stove enclosing the latter at the end of the tube 9 to be heated to a temperature, slightly, preferably less than 50 C. above the conversion temperature of glass, and then for the edge of the face plate to be progressively welded onto the edge of the tube 19 by the needle flame while the glass bulb is slowly rotated.

It should be noted that for the sake of simplicity auxiliary means on the electrodes, such as evaporating means to produce a film of antimony or bismuth on the plate 19, and means for developing alkali vapour, have not been shown in the drawings. Manufacture of the tube is completed in the same manner, the beam system mounted at the foot of the tube being inserted into the neck of the tube and the foot and neck being fused together. The tube can then be evacuated, and the photocathode and beam cathode developed by the usual methods.

What is claimed as new and desired to be secured by Letters Patent is:

1. The process of making an image orthicon tube having an active target portion at least equal to the diameter of the neck of the tube, the said process comprising the steps of inserting the image converter electrodes into a glass tube assembly having a wide diameter substantially cylindrical portion for housing the said converter electrodes and a narrow diameterportion for housing the cathode ray producing electrodes, the insertion being effected through the said wide diameter portion; then securing each of the said converter electrodes directly to the inner wall of said wide diameter portion by cooperating notches and projections on said converter electrodes and inner wall of the tube portion; and thereafter closing the outside end of the wide diameter portion by a face late. P 2. The process of claim 1, wherein the said glass tube assembly is made of a separate wide diameter portion and narrow diameter portion and wherein the two tube portions are fused together prior to the insertion of said image converter electrodes into the wide diameter portion.

3. The process of claim 2, wherein the wide diameter portion is fused to an end flange on the narrow diameter tube portion.

4. The process of claim 1, wherein a field mesh is in sorted through the open end of the wide diameter tube portion before the target is introduced.

5. The process of claim 1, wherein the image converter electrodes are secured to the inner wall of the wide diameter tube portion by snapping projecting spring parts on said converter electrodes into place in corresponding notches on said inner wall of the tube portion.

6. The process of claim 3, wherein the image converter electrodes are electrically connected by welding them to flexible lead-in wires extending through the flange of the narrow diameter tube portion after securing the electrodes to the wall of said wide diameter portion.

7. The process of claim 6, wherein the face plate is brought into electrical contact with the lead-in wires by establishing a resilient wire connection between the said lead-in wires and a metallized portion on said face plate.

8. The process of claim 1, wherein the face plate is secured to the wide diameter tube portion by circular welding while rotating its bevelled rim relative to said wide diameter tube portion.

9. The process of claim 8, wherein the open end of the wide diameter tube portion and the face plate are placed in an oven during the welding operation, the temperature during the welding being kept at a level below 50 C. above the softening point of the glass.

10. The process of claim 9, wherein the image converter electrodes are individually inserted in said wide diameter tube portion and then individually secured to said inner wall of said wide diameter tube portion.

11. The process of making an image orthicon tube having a bulb comprising a neck portion for housing the cathode ray producing elements and a tube portion of wider diameter than said neck portion for housing the image converter electrodes including a target electrode having an active target portion at least equal to the diamter of said neck portion, comprising the steps of forming in said tube portion of wider diameter a plurality of sets of notches axially spaced from each other with the notches of each set circumferentially spaced from each other and each notch extending from the inner surface of said tube portion short of the outer surface thereof; individually introducing said image converter electrodes through the open end of said wide diameter portion into the latter;

introducing a field mesh likewise through said open end into said wider diameter portion before introducing said target electrode thereinto; and securing said image converter electrodes and said field mesh individually directed to the wall of said tube portion by snapping projecting 5 6 spring parts on said image converter electrodes and said 2,728,009 12/1955 Faulkner et a1. 2925.15 XR field mesh respectively into said sets of notches. 2, 45,143 7/1960 Shapiro 2925.16 XR 3,202,856 8/1965 Davis 31365 References Cited FOREIGN PATENTS UNITED STATES PATENTS 5 699,175 11/ 195 3 Great Britain. 2,168,892 8/1939 Zworykm 2925.15 XR 2 3 6 35 193 Australia 2,820,212 1/1958 Batcheller 339-91 2,959,850 11/ 1960 Deringer 2945 8 JOHN F. CAMPBELL, Primary Examiner 2,959,851 11/1960 Deringer 29458 2,994,798 8/1961 Krieger 6118.1 31365 10 LAZARUS Assstant Exammer 3,146,051 8/1964 Woofter et a1. 339-91 CL 3,303,373 2/1967 Alting-Mees 313-65 29-25.13; 2202.1 

